I have a Samsung Series 7 NP700-Z5A, which has a dual-purpose mic/headphone jack.
In both Ubuntu 12.04 and Windows 7, whenever I plug in my headphones the internal mic goes completely dead. When the headphones aren't plugged in, the microphone is fine.
The hardware is Realtek HD audio and the driver version 6.0.1.6428 (on Windows, at least).
I have an inkling that it thinks my headphones are a microphone, but there seems to be no option (in either OS) to adjust this.
Why can't I use my laptop's internal microphone while my headphones are plugged in?
Best Answer
I was able to fix the internal microphone in Realtek HD Audio Manager:
Open Control Panel → Hardware and Sound → Realtek HD Audio Manager.
In Realtek Audio Manager, select "Device advanced settings" in the top right.
Select "Separate all input jacks as independent devices" and click OK.
(If you don't see an option to separate jacks, you may need to update your Realtek Audio drivers.)
Open Control Panel → Hardware and Sound → Sound → Recording
Set your internal microphone as the default recording device.